The invention relates to an apparatus for analyzing particles such as cells contained in liquid samples of blood, urine and the like, or particles moving in a gas, and more specifically, for example, to an apparatus for analyzing particles capable of obtaining morphological information or light absorption information of individual particles in real time, by illuminating particles such as cells, with light and focusing the transmitted light images on a photo detector in which photo detecting elements are arranged in lines.
By attaching (adding) such apparatus to, for example, a conventional flow cytometer, particles can be judged at higher precision, resulting in an apparatus for analyzing particles of higher reliability.
An apparatus designed to obtain more specific morphological information for individual particles by optically scanning a laser beam reduced narrowly to the particles flowing in the sheath flow in a direction intersecting the flow direction of particles, and obtaining optical signals from parts of particles to be analyzed is known. Herein, the sheath flow refers to a flow having the surroundings of a suspension of particles covered with a sheath liquid of laminar flow in order to pass particles by arranging them in a row precisely in the middle part of the flow.
As the apparatuses for analyzing by extracting the features of particles moving in a fluid flow cytometer and cell sorter are known.
The Japanese Patent Publication Hei. 3-52573 (corresponding to U.S. Pat. No. 4,338,024) discloses an apparatus for forming a flat sheath flow and picking up particle images.
In the conventional flow cytometer, morphological information of particles (area, circumference length, etc.) could not be obtained. Besides, by processing particle images picked up by a video camera, in order to obtain the light absorption (extinction) quantity of each particle and morphological information in real time, an expensive video camera, and a high-performance and expensive exclusive image processor were needed. Moreover, because of the mechanism of picking up by emitting strobe light at specific intervals in one frame period (1/30 sec) of the video camera, particles of low concentration could not be completely captured on the pickup screen of the video camera efficiently, and there were problems in the specimen processing capacity and repeatability of analysis results.
Many proposals have been already disclosed about the apparatus for analyzing flowing particles by scanning a narrowly reduced light beams at high speed, but nothing has been clearly disclosed about how to process optical signals obtained by scanning light beams to obtain morphological information of particles, and how to determine the information in real time every time a particle passes the detecting unit.
The present applicant has already developed an apparatus for analyzing particles capable of determining the morphological information and light absorption quantity of individual particles in real time by adding a detecting system by line sensor (one-dimensional image sensor) and its signal processing system, and scanning the images of particles flowing in a flat sheath flow cell, and applied for patents (Japanese Patent Applications Hei. 3-270106, Hei. 3-270107). However, the sample flow velocity in this apparatus cannot be raised sufficiently because of the relation with the scan cycle time of line sensor and image resolution in the particle flow direction, and the maximum speed was 100 mm/sec, which was about 1/50 that of the conventional flow cytometer. If the sample flow is a flat flow of 100 to 200 .mu.m in width, the analysis quantity per unit time is only 1/5 to 1/10.
In order to increase the number of particles to be analyzed, there is known a method of decreasing the sample dilution factor (raising the particle concentration), and heightening the concentration of particles contained in the sample flow, but the problem is not solved if the sample itself is low in particle density, such as urine samples, or enough sample volume is not obtained.
Besides, when the sample flow is transformed to a flat flow, the probability is high that two or more particles may pass the detecting area of the line sensor simultaneously, which means that plural sets of calculators are needed for obtaining various morphological information or light absorption quantity, and moreover processing the region division is complicated in order to discriminate the individual particles passing very closely to each other.
Thus, in the conventional line sensor (one-dimensional image sensor), since the output signals from the elements were produced in series, particles could not be passed at high speed, and the particle images were blurry, and hence it took a long time in signal processing, too.